ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
A concentric cylinder viscometer was used to measure high shear viscosities of polyisobutene solutions. Data were obtained in laminar flow from 20-100°C. and at shear rates from 5 × 102 to 8 × 105 sec.-1. Three polymer molecular weights, 4.0 × 104-2.2 × 106, in three concentrations from 11.5-49.2 wt.-% polymer were tested in cetane. The viscosity of cetane at all test temperatures was low and independent of shear rate up to 106 sec.-1. Therefore, variations in viscosity with shear were due totally to the effect of polymer. Viscosities of 11.5% solutions of low molecular weight polyisobutene, 4-6 × 104, approached limiting viscosities at both high and low rates of shear. Viscosity changed markedly between the limiting values as did the flow activation energy at constant shear rate, ΔE*r. At extremes of both high and low shear rate ΔE*r appeared to be insensitive to polymer molecular weight. Solutions containing the highest molecular weight and concentration of polyisobutene reached shear stresses for polymer degradation before a limiting high shear viscosity could be observed. For all solutions, ΔE*r was independent of temperature form 20-100°C. At low shear, ΔE*r increased with polymer concentration. At high shear, the concentration dependence was reversed, with the highest concentration having the lowest ΔE*r. A simple shear correlation was found to superimpose all data for which reduced viscosities could be derived. Reduced specific viscosities superimposed on a master curve when plotted against log (shear stress/T°K). The correlation covered data at all temperatures and concentrations for the two lower molecular weight polymer solutions.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1960.070030715
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